Expression of granular starch hydrolyzing enzyme in Trichoderma

ABSTRACT

The present invention relates to filamentous fungal host cells and particularly  Trichoderma  host cells useful for the production of heterologous granular starch hydrolyzing enzymes having glucoamylase activity.

The present application is a divisional of U.S. patent application Ser.No. 11/633,309, filed Dec. 4, 2006, now U.S. Pat. No. 7,335,503 which isa Continuation of U.S. patent application Ser. No. 10/992,187, filedNov. 18, 2004, now U.S. Pat. No. 7,262,041, which claims priority toU.S. Provisional Patent Appln. Ser. No. 60/524,279, filed Nov. 21, 2003;U.S. Provisional Patent Appln. No. 60/531,953, filed Dec. 22, 2003; andU.S. Provisional Patent Appln. No. 60/566,358, filed Apr. 28, 2004.

FIELD OF THE INVENTION

The present invention relates to filamentous fungal host cells usefulfor the production of granular starch hydrolyzing enzymes havingglucoamylase activity (GSHE), wherein the GSHE is derived from a strainof Humicola grisea or a strain of Aspergillus awamori. Morespecifically, the invention relates to the expression of a heterologouspolynucleotide encoding a GSHE in a Trichoderma host and particularly ina Trichoderma reesei host.

BACKGROUND OF THE INVENTION

Industrial fermentations predominately use glucose as a feed stock forthe production of a multitude of proteins, enzymes, alcohols and otherchemicals. In many applications, the glucose is produced by theenzymatic conversion of starch. This conversion is frequentlyaccomplished by a two-step process. The first step is a liquefactionstep, wherein an insoluble granular starch substrate is slurried inwater, gelatinized with heat and hydrolyzed by a thermostable alphaamylase (e.g., E.C. 3.2.1.1: 1,4-alpha-D-glucan glucoanohydrolase) inthe presence of calcium. The second step is a saccharification step,wherein the soluble dextrins (sugars) produced in the first step arefurther hydrolyzed to glucose by an enzyme having glucoamylase (e.g.,E.C. 3.2.1.3: 1,4-alpha-D-glucan glucohydrolase) activity. Glucoamylasescatalyze the release of glucose from the non-reducing ends of starch.Glucose may then be used as an end product or used as a precursor to beconverted to other commercially important end products, such asfructose, ethanol, ascorbic acid (ASA) intermediates and/or1,3-propanediol.

Therefore, glucoamylases, which are involved in the conversion of starchto sugar are extremely important industrial enzymes. Glucoamylases maybe obtained from bacteria, plants and fungi. However, preferredglucoamylases are derived from fungal strains. Examples of fungalglucoamylases include those obtained from strains of Aspergillus,Rhizopus, Humicola and Mucor (See, WO 92/00381 and WO 00/04136).

Various glucoamylases have been commercialized, including Aspergillusnigerglucoamylase (e.g., trade name OPTIDEX L-400® from GenencorInternational Inc. and trade name AMG from Novo Nordisk) and Rhizopus(e.g., trade name CU.CONC from Shin Nihon Chemicals, Japan and tradename GLUCZYME from Amano Pharmaceuticals, Japan).

Certain thermophilic and mesophilic fungi, and particularly strains ofHumicola grisea and Aspergillus awamori, produce an enzyme having bothglucoamylase activity and the ability to hydrolyze raw starch. Theseglucoamylases are referred to as granular starch hydrolyzing enzymes(GSHE) and are also known in the art as raw starch hydrolyzing (RSH)enzymes. Additionally, while these enzymes will hydrolyze thinned starchhydrolyzate to glucose in a manner similar to other known glucoamylases,they frequently have a pH optimum in the range of 5.0 to 7.0 as comparedto a pH optimum of less than 5.0 for widely used glucoamylasepreparations (See, Tosi et al., (1993) Can. J. Microbiol., 39: 846-851).

BRIEF SUMMARY OF THE INVENTION

Since glucoamylases and in particular granular starch hydrolyzingenzymes are important enzymes used industrially for the conversion ofstarch to glucose, processes providing increased expression andproduction of these enzymes are highly desirable. In addition, granularstarch hydrolyzing enzymes having improved characteristics, such asincreased specific activity, different pH ranges, and/or differentlevels of glycosylation may be particularly advantageous in industrialprocesses.

It is a primary object of this invention to provide a filamentous fungalstrain transformed with a heterologous polynucleotide encoding agranular starch hydrolyzing enzyme, especially a Trichoderma strain andmore specifically a strain of T. reesei, which expresses and secretesgranular starch hydrolyzing enzyme into its culture medium.

In one aspect, the invention provides a recombinant Trichoderma cellcomprising a heterologous polynucleotide encoding a granular starchhydrolyzing enzyme (GSHE). In one embodiment, the recombinantTrichoderma cell includes a heterologous polynucleotide encoding a GSHEhaving at least 80% sequence identity to the sequence set forth in SEQID NO: 3 or the sequence set forth in SEQ ID NO: 6. In a secondembodiment, the recombinant Trichoderma cell includes a heterologouspolynucleotide encoding a GSHE having at least 90% sequence identity tothe sequence set forth in SEQ ID NO: 3 or the sequence set forth in SEQID NO: 6. In a third embodiment, the recombinant Trichoderma cellincludes a heterologous polynucleotide encoding a GSHE having at least95% sequence identity to the sequence set forth in SEQ ID NO: 3 or thesequence set forth in SEQ ID NO: 6. In a fourth embodiment, therecombinant Trichoderma cell includes a heterologous polynucleotideencoding a GSHE having the sequence set forth in SEQ ID NO: 3 or thesequence set forth in SEQ ID NO: 6. In another embodiment, therecombinant Trichoderma cell includes a heterologous polynucleotideencoding a GSHE wherein the polynucleotide has at least 90% sequenceidentity with the sequence set forth in SEQ ID NO: 1 or the sequence setforth in SEQ ID NO: 4. In another embodiment, the recombinantTrichoderma cell includes a heterologous polynucleotide encoding a GSHEwherein the polynucleotide has the sequence set forth in SEQ ID NO: 1 orthe sequence set forth in SEQ ID NO: 4. In a preferred embodiment, therecombinant Trichoderma cell is a T. reesei cell. In certain embodimentsof this aspect the heterologous polynucleotide encodes a GSHE that isexpressed at a level of greater than 1 g/L.

In a second aspect, the invention provides methods for producing arecombinantly expressed granular starch hydrolyzing enzyme (GSHE) in afilamentous fungal cell which comprises cultivating in a suitableculture medium a filamentous fungal host cell transformed with a DNAconstruct comprising a promoter having transcriptional activity in thefilamentous fungal host cell operably linked to a heterologouspolynucleotide encoding a GSHE wherein said GSHE is expressed in thetransformed fungal cell, and recovering the expressed GSHE. In someembodiments, the filamentous fungal host cell is selected from the groupconsisting of Aspergillus, Fusarium, Penicillium and Trichoderma. Infurther preferred embodiments the fungal host cell is a Trichodermacell, particularly a T. reesei cell. In other embodiments, the fungalhost cell is an Aspergillus cell, particularly an A. awamori, A. nigeror A. oryzae cell. In another embodiment, the promoter is derived from agene of the filamentous fungal host. In a further embodiment, thepolynucleotide encoding the GSHE is derived from a strain of Humicolagrisea or a strain of Aspergillus awamori. In yet another embodiment,the heterologous GSHE produced by the host fungal cell has at least 80%sequence identity with the polypeptide sequence of SEQ ID NO: 3 or withthe polypeptide sequence of SEQ ID NO: 6. In other embodiments, theheterologous GSHE produced by the host fungal cell has at least 95%sequence identity with the polypeptide sequence of SEQ ID NO: 3 or withthe polypeptide sequence of SEQ ID NO: 6. In further embodiments, thepolynucleotide sequence encoding the GSHE has at least 90% sequenceidentity with the sequence of SEQ ID NO: 1 or SEQ ID NO: 4. In furtherembodiments, the recombinantly expressed GSHE is encoded by thepolynucleotide of SEQ ID NO: 1 or the polynucleotide SEQ ID NO: 4. Inanother embodiment, the level of glycosylation of the recombinantlyexpressed GSHE is different from the level of glycosylation of thecorresponding native GSHE. In some embodiments, the level ofglycosylation of the recombinantly expressed GSHE is less than the levelof glycosylation of the corresponding native GSHE. A further embodimentprovides enzymatic compositions comprising the GSHE produced accordingto the method.

In a third aspect, the invention provides a vector comprising apromoter, a granular starch hydrolyzing enzyme (GSHE) signal sequence, apolynucleotide encoding a mature GSHE and a terminator, wherein thepromoter and terminator are each functional in a Trichoderma cell andare derived from a filamentous fungus and the polynucleotide encodingthe GSHE is derived from Humicola grisea or Aspergillus awamori. In oneembodiment, the vector is the plasmid pTrex3g_N13. In a secondembodiment the invention provides a Trichoderma host cell transformedwith the vector.

In a fourth aspect, the invention provides a granular starch hydrolyzingenzyme (GSHE) fraction obtained from a substantially pure culture ofTrichoderma reesei, wherein the Trichoderma reesei comprises aheterologous polynucleotide encoding a GSHE. In one embodiment, the GSHEenzyme fraction includes a GSHE having at least 80% amino acid sequenceidentity with SEQ ID NO: 3 or a GSHE having at least 80% amino acidsequence identity with SEQ ID NO: 6.

In a fifth aspect, the invention provides, methods for producing agranular starch hydrolyzing enzyme (GSHE) in a Trichoderma reesei hostcell comprising transforming a Trichoderma reesei host cell with a DNAconstruct, wherein the DNA construct comprises a promoter showingtranscriptional activity in Trichoderma reesei and which is operablylinked to DNA encoding a heterologous GSHE and culturing the transformedTrichoderma reesei host cell under suitable culture conditions to allowproduction of the heterologous GSHE. In one embodiment, the DNA encodingthe heterologous GSHE has at least 95% sequence identity with SEQ ID NO:1 and in other embodiment the DNA encoding the heterologous GSHE has atleast 95% sequence identity with SEQ ID NO: 4. In a second embodiment,the method further comprises recovering the GSHE enzyme. In anotherembodiment, the DNA sequence encoding the heterologous GSHE enzyme isderived from Humicola grisea or Aspergillus awamori. In someembodiments, the GSHE produced by the transformed T. reesei host cellhas at least 80% amino acid sequence identity with SEQ ID NO: 3, and inother embodiments the GSHE produced by the transformed T. reesei hostcell has at least 80% amino acid sequence identity with SEQ ID NO: 6. Afurther embodiment provides for the Trichoderma obtained according tothe method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides the genomic DNA sequence coding for the native H. griseavar. thermoidea GSHE (SEQ ID NO: 1). The putative introns are in boldand underlined.

FIG. 2A provides the signal sequence and mature amino acid sequence forH. grisea var. thermoidea GSHE (SEQ ID NO: 2). The putative signalsequence is in bold and underlined.

FIG. 2B provides the mature amino acid sequence for H. grisea var.thermoidea GSHE (SEQ ID NO: 3).

FIG. 3 provides a map of pTrex3g_N13 plasmid, which was used forexpression of the nucleic acid encoding the Humicola grisea GSHE andwhich contains the Xba1 sites flanking the fungal expression vectorwherein

-   -   a) cbh1 promoter is the Trichoderma reesei cellobiohydrolase        promoter,    -   b) H. grisea gla1 is the polynucleotide encoding the Humicola        grisea GSHE of SEQ ID NO:3,    -   c) cbh1 terminator is the Trichoderma reesei cellobiohydrolase        terminator and    -   d) amdS is an Aspergillus nidulans acetamidase marker gene.

FIGS. 4A-4E provide the nucleotide sequence (SEQ ID NO: 11) (10738 bp)of the pTrex3g_N13 plasmid of FIG. 3.

FIG. 5 provides an SDS-PAGE gel indicating the expression of H. griseavar. thermoidea GSHE in a representative fermentation run forTrichoderma reesei clones as described in Example 3. Lane 1 representsthe commercial molecular weight marker, SeeBlue (Invitrogen); lane 2 isblank, lane 3 depicts rGSHE expression at 48 hours, lane 4 depicts rGSHEexpression at 56 hours and lane 5 depicts rGSHE expression at 64 hours.

FIG. 6 provides the genomic DNA sequence coding for the Aspergillusawamori var. kawachi GSHE (SEQ ID NO:4). The putative introns are inbold and underlined.

FIG. 7A provides the signal sequence and mature amino acid sequence forA. awamori var. kawachi GSHE (SEQ ID NO:5). The signal sequence is inbold and underlined.

FIG. 7B provides the mature amino acid sequence for Aspergillus awamorivar. kawachi GSHE (SEQ ID NO:6).

FIGS. 8A and 8B illustrate the pH stability as % residual activity forthe native Humicola grisea var. thermoidea GSHE (nGSHE) and theexpressed H. grisea var. thermoidea GSHE (rGSHE) in the T. reesei host(SEQ ID NO:3), as described in Example 5.

FIG. 9 illustrates the hydrolysis of corn starch measured as mgglucose/mg protein over time for native Humicola grisea var. thermoideaGSHE and the expressed H. grisea var. thermoidea GSHE in the recombinantT. reesei host, as described in Example 5.

FIG. 10 provides an SDS-PAGE gel indicating the expression ofAspergillus awamori var. kawachi GSHE in a representative fermentationrun for Trichoderma reesei clones as described in Example 7. Lane 1represents the commercial molecular weight marker, SeeBlue (Invitrogen);lane 2 depicts rGSHE expression at 162 hours, and lane 3 is a controlwhich depicts the untransformed Trichoderma reesei host at 162 hours.

DETAILED DESCRIPTION OF THE INVENTION

In some aspects, the present invention relies on routine techniques andmethods used in the field of genetic engineering and molecular biology.The following resources include descriptions of general methodologyuseful in accordance with the invention: Sambrook et al., MOLECULARCLONING: A LABORATORY MANUAL (2nd Ed., 1989); Kreigler, GENE TRANSFERAND EXPRESSION; A LABORATORY MANUAL (1990) and Ausubel et al., Eds.CURRENT PROTOCOLS IN MOLECULAR BIOLOGY (1994).

Unless defined otherwise herein, all technical and scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which this invention belongs. Singleton, et al.,DICTIONARY OF MICROBIOLOGY AND MOLECULAR BIOLOGY, 2D ED., John Wiley andSons, New York (1994), and Hale & Markham, THE HARPER COLLINS DICTIONARYOF BIOLOGY, Harper Perennial, N.Y. (1991) provide one of skill with ageneral dictionary of many of the terms used in this invention. Althoughany methods and materials similar or equivalent to those describedherein can be used in the practice or testing of the present invention,the preferred methods and materials are described.

The invention will now be described in detail by way of reference onlyusing the following definitions and examples. All patents andpublications, including all sequences disclosed within such patents andpublications, referred to herein are expressly incorporated byreference.

Numeric ranges are inclusive of the numbers defining the range.

Unless otherwise indicated, nucleic acids are written left to right in5′ to 3′ orientation; amino acid sequences are written left to right inamino to carboxy orientation, respectively.

The headings provided herein are not limitations of the various aspectsor embodiments of the invention which can be had by reference to thespecification as a whole.

Definitions

The term “glucoamylase” refers to the amyloglucosidase class of enzymes(e.g., EC.3.2.1.3, glucoamylase, 1,4-alpha-D-glucan glucohydrolase).These are exo-acting enzymes which release glucosyl residues from thenon-reducing ends of amylose and amylopectin molecules. The enzyme alsohydrolyzes alpha-1,6 and alpha-1,3 linkages although at much slowerrates than alpha-1,4 linkages.

The term “granular starch hydrolyzing enzyme (GSHE)” as used hereinspecifically refers to a glucoprotein which has glucoamylase activityand has the ability to hydrolyze starch in granular form. A preferredGSHE is derived from Humicola grisea var. thermoidea. Another preferredGSHE is derived from Aspergillus awamori var. kawachi. In preferredembodiments, the GSHE is expressed in a Trichoderma strain, particularlya T. reesei strain. In particularly preferred embodiments, GSHE isexpressed as an extracellular enzyme.

The term “glycosylation” refers to the post-transcriptional modificationof a protein by the addition of carbohydrate moieties, wherein thecarbohydrate is either N-linked or O-linked resulting in a glucoprotein.An N-linked carbohydrate moiety of a glycoprotein is attached by aglycosidic bond to the β-amide nitrogen of an asparagine residue. AnO-linked carbohydrate is attached by a glycosidic bond to a proteinthrough the hydroxy group of a serine or a threonine residue.

The term “recombinant” when used in reference to a cell, nucleic acid,protein or vector, indicates that the cell, nucleic acid, protein orvector, has been modified by the introduction of a heterologous nucleicacid or protein or the alteration of a native nucleic acid or protein,or that the cell is derived from a cell so modified. Thus, for example,recombinant cells express genes that are not found within the native(non-recombinant) form of the cell or express native genes that areotherwise abnormally expressed, under expressed or not expressed at all.

The terms “protein” and “polypeptide” are used interchangeably herein.The conventional one-letter or three-letter code for amino acid residuesis used herein.

A “signal sequence” means a sequence of amino acids bound to theN-terminal portion of a protein which facilitates the secretion of themature form of the protein outside the cell. The definition of a signalsequence is a functional one. The mature form of the extracellularprotein lacks the signal sequence which is cleaved off during thesecretion process.

The terms “recombinant GSHE”, “recombinantly expressed GSHE” and“recombinantly produced GSHE” refer to a mature GSHE protein sequencethat is produced in a host cell from a heterologous polynucleotide. Thesymbol “r” may be used to denote “recombinant”. The protein sequence ofa rGSHE excludes a signal sequence.

The terms “native GSHE” and “nGSHE” refer to a GSHE that is derived froma microbial host other than the fungal host for which recombinant GSHEexpression is desired. In preferred embodiments, a native GSHE isderived from a Humicola grisea strain or an Aspergillus awamori strain.

A “gene” refers to a DNA segment that is involved in producing apolypeptide and includes regions preceding and following the codingregions as well as intervening sequences (introns) between individualcoding segments (exons).

The term “nucleic acid” encompasses DNA, RNA, single stranded or doublestranded and chemical modifications thereof. The terms “nucleic acid”and “polynucleotide” may be used interchangeably herein. Because thegenetic code is degenerate, more than one codon may be used to encode aparticular amino acid, and the present invention encompassespolynucleotides which encode a particular amino acid sequence.

A “vector” refers to a polynucleotide sequence designed to introducenucleic acids into one or more cell types. Vectors include cloningvectors, expression vectors, shuttle vectors, plasmids, phage particles,cassettes and the like.

An “expression vector” as used herein means a DNA construct comprising aDNA sequence which is operably linked to a suitable control sequencecapable of effecting expression of the DNA in a suitable host. Suchcontrol sequences may include a promoter to effect transcription, anoptional operator sequence to control transcription, a sequence encodingsuitable ribosome binding sites on the mRNA, enhancers and sequenceswhich control termination of transcription and translation.

A “promoter” is a regulatory sequence that is involved in binding RNApolymerase to initiate transcription of a gene. The promoter may be aninducible promoter or a constitutive promoter. A preferred promoter usedin the invention is Trichoderma reesei cbh1, which is an induciblepromoter.

“Under transcriptional control” is a term well understood in the artthat indicates that transcription of a polynucleotide sequence, usuallya DNA sequence, depends on its being operably linked to an element whichcontributes to the initiation of, or promotes transcription.

“Under translational control” is a term well understood in the art thatindicates a regulatory process which occurs after mRNA has been formed.

As used herein when describing proteins and genes that encode them, theterm for the gene is not capitalized and is italicized, (e.g., the genethat encodes the Humicola grisea GSHE may be denoted as gla1). The termfor the protein is generally not italicized and the first letter iscapitalized, (e.g., the protein encoded by the gla1 gene may be denotedas Gla1).

The term “operably linked” refers to juxtaposition wherein the elementsare in an arrangement allowing them to be functionally related. Forexample, a promoter is operably linked to a coding sequence if itcontrols the transcription of the sequence.

The term “selective marker” refers to a gene capable of expression in ahost that allows for ease of selection of those hosts containing anintroduced nucleic acid or vector. Examples of selectable markersinclude but are not limited to antimicrobials (e.g., hygromycin,bleomycin, or chloramphenicol) and/or genes that confer a metabolicadvantage, such as a nutritional advantage on the host cell.

The term “derived” encompasses the terms “originated from”, “obtained”or “obtainable from”, and “isolated from”.

“Host strain” or “host cell” means a suitable host for an expressionvector or DNA construct comprising a polynucleotide encoding a GSHEaccording to the invention. Specifically, host strains are preferablyfilamentous fungal cells. In a preferred embodiment of the invention,“host cell” means both the cells and protoplasts created from the cellsof a filamentous fungal strain and particularly a Trichoderma sp. or anAspergillus sp.

The term “filamentous fungi” refers to all filamentous forms of thesubdivision Eumycotina (See, Alexopoulos, C. J. (1962), INTRODUCTORYMYCOLOGY, Wiley, New York). These fungi are characterized by avegetative mycelium with a cell wall composed of chitin, cellulose, andother complex polysaccharides. The filamentous fungi of the presentinvention are morphologically, physiologically, and genetically distinctfrom yeasts. Vegetative growth by filamentous fungi is by hyphalelongation and carbon catabolism is obligatory aerobic. In the presentinvention, the filamentous fungal parent cell may be a cell of a speciesof, but not limited to, Trichoderma, (e.g., Trichoderma reesei(previously classified as T. longibrachiatum and currently also known asHypocrea jecorina), Trichoderma viride, Trichoderma koningii,Trichoderma harzianum); Penicillium sp., Humicola sp. (e.g., Humicolainsolens and Humicola grisea); Chrysosporium sp. (e.g., C. lucknowense),Gliocladium sp., Aspergillus sp. (e.g., A. oryzae, A. niger, and A.awamori), Fusarium sp., Neurospora sp., Hypocrea sp., and Emericella sp.(See also, Innis et al., (1985) Sci. 228:21-26).

As used herein, the term “Trichoderma” or “Trichoderma sp.” refer to anyfungal genus previously or currently classified as Trichoderma.

The term “culturing” refers to growing a population of microbial cellsunder suitable conditions in a liquid or solid medium.

The term “heterologous” with reference to a polynucleotide or proteinrefers to a polynucleotide or protein that does not naturally occur in ahost cell. In some embodiments, the protein is a commercially importantindustrial protein. It is intended that the term encompass proteins thatare encoded by naturally occurring genes, mutated genes, and/orsynthetic genes. The term “homologous” with reference to apolynucleotide or protein refers to a polynucleotide or protein thatoccurs naturally in the host cell.

The terms “recovered”, “isolated”, and “separated” as used herein referto a protein, cell, nucleic acid or amino acid that is removed from atleast one component with which it is naturally associated.

As used herein, the terms “transformed”, “stably transformed” and“transgenic” used in reference to a cell means the cell has a non-native(e.g., heterologous) nucleic acid sequence integrated into its genome oras an episomal plasmid that is maintained through multiple generations.

As used herein, the term “expression” refers to the process by which apolypeptide is produced based on the nucleic acid sequence of a gene.The process includes both transcription and translation.

The term “introduced” in the context of inserting a nucleic acidsequence into a cell, means “transfection”, or “transformation” or“transduction” and includes reference to the incorporation of a nucleicacid sequence into a eukaryotic or prokaryotic cell wherein the nucleicacid sequence may be incorporated into the genome of the cell (e.g.,chromosome, plasmid, plastid, or mitochondrial DNA), converted into anautonomous replicon, or transiently expressed (e.g., transfected mRNA).

As used herein the term “specific activity” means an enzyme unit definedas the number of moles of substrate converted to product by an enzymepreparation per unit time under specific conditions. Specific activityis expressed as units (U)/mg of protein.

As used herein the term “enzyme unit” refers to the amount of enzymethat converts 1 micromole of substrate per minute to the substrateproduct at optimum assay conditions. For example, in one embodiment, theterm “glucoamylase activity unit” (GAU) is defined as the amount ofenzyme required to produce 1 micromole of glucose per minute under assayconditions of, for example 40° C. and pH 5.0. In another embodiment, agranular starch hydrolyzing enzyme unit (GSHE U) is defined as being theamount of GSHE required to produce 1 g of glucose per minute fromgranular starch under assay conditions of, for example 25° C. at pH 5.0.In another embodiment a GSHE U is defined as being the amount of GSHErequired to produce 1 mg of glucose per minute from granular starchunder assay conditions, of 50° C. at pH 4.5.

As used herein the term “starch” refers to any material comprised of thecomplex polysaccharide carbohydrates of plants, comprised of amylose andamylopectin with the formula (C₆H₁₀O₅)_(x), wherein X can be any number.In particular, the term refers to any plant-based material including butnot limited to grains, grasses, tubers and roots and more specificallyto the plants wheat, barley, corn, rye, rice, sorghum, brans, cassava,millet, potato, sweet potato, and tapioca.

The term “granular starch” refers to raw uncooked starch, e.g., granularstarch that has not been subject to gelatinization.

The term “starch-liquefying enzyme” refers to an enzyme that effects thefluidization of granular starch. Exemplary starch liquefying enzymesinclude alpha amylases (e.g., E.C. 3.2.1.1).

The term “alpha-amylase (e.g., E.C. class 3.2.1.1)” refers to enzymesthat catalyze the hydrolysis of alpha-1,4-glucosidic linkages. Theseenzymes have also been described as those effecting the exo orendohydrolysis of 1,4-α-D-glucosidic linkages in polysaccharidescontaining 1,4-α-linked D-glucose units. Another term used to describethese enzymes is “glycogenase”. Exemplary enzymes includealpha-1,4-glucan 4-glucanohydrase glucanohydrolase.

“ATCC” refers to American Type Culture Collection located at Manassas,Va. 20108 (ATCC; www.atcc.org).

“NRRL” refers to the Agricultural Research Service Culture Collection,National Center for Agricultural Utilization Research (and previouslyknown as USDA Northern Regional Research Laboratory), Peoria, ILL.

“A”, “an” and “the” include plural references unless the context clearlydictates otherwise.

As used herein the term “comprising” and its cognates are used in theirinclusive sense; that is, equivalent to the term “including” and itscorresponding cognates.

Preferred Embodiments

Host Organisms

The present invention provides host cells, which can express aheterologous polynucleotide encoding a GSHE. The host cell is preferablya filamentous fungal cell. In a preferred embodiment, the filamentousfungal host is a strain of Aspergillus sp, Trichoderma sp, Fusarium spand Penicillium sp. Particularly preferred fungal host cells include A.nidulans, A. awamori, A. oryzae, A. aculeatus, A. niger, A. japonicus,T. reesei, T. viride, F oxysporum, and F. solani. Aspergillus strainsare disclosed in Ward et al. (1993) Appl. Microbiol. Biotechnol.39:738-743 and Goedegebuur et al., (2002) Curr Gene 41:89-98. In a mostpreferred embodiment, the host is a strain of Trichoderma andparticularly a strain of T. reesei. Strains of T. reesei are known andnonlimiting examples include ATCC No. 13631, ATCC No. 26921, ATCC No.56764, ATCC No. 56765, ATCC No. 56767 and NRRL 15709. In some preferredembodiments, the host strain is a derivative of RL-P37. RL-P37 isdisclosed in Sheir-Neiss et al. (1984) Appl Microbiol. Biotechnology20:46-53.

The host strain may be previously manipulated through geneticengineering. In some embodiments, various native genes of the fungalhost cell have been inactivated. These genes include, for example genesencoding cellulolytic enzymes, such as endoglucanases (EG) andexocellobiohydrolases (CBH) (e.g. cbh1, cbh2, eg/1 and eg/3). U.S. Pat.No. 5,650,322 discloses derivative strains of RL-P37 having deletions inthe cbh1 gene and the cbh2 gene.

B. Glucoamylases and Granular Starch Hydrolyzing Enzymes

In the context of this invention, a glucoamylase (E.C. 3.2.1.3) is anenzyme that removes successive glucose units from the non-reducing endsof starch. The enzyme can hydrolyze both linear and branched glucosidiclinkages of starch, amylose and amylopectin. While glucoamylase may bederived from bacteria, plants and fungi, preferred glucoamylasesencompassed by the present invention are derived from fungal strains.Glucoamylases secreted from fungi of the genera Aspergillus, Rhizopus,Humicola and Mucor have been derived from various fungal strains,including Aspergillus niger, Aspergillus awamori, Rhizopus niveus,Rhizopus oryzae, Mucor miehe, Humicola grisea, Aspergillus shirousamiand Humicola (Thermomyces) laniginosa (See, Boel et al., (1984) EMBO J.3:1097-1102; WO 92/00381; WO 00/04136; Chen et al., (1996) Prot. Eng.9:499-505; Taylor et al., (1978) Carbohydrate Res. 61:301-308 and Jensenet al., (1988) Can. J. Microbiol. 34:218-223).

A particular group of enzymes having glucoamylase activity are known asgranular starch hydrolyzing enzyme(s) GSHE (See e.g., Tosi et al.,(1993) Can. J. Microbiol. 39:846-855). GSHEs not only have glucoamylaseactivity, but also are able to hydrolyze granular (raw) starch. GSHEshave been recovered from fungal cells such as Humicola sp., Aspergillussp. and Rhizopus sp. A Rhizopus oryzae GSHE has been described inAshikari et al., (1986) Agric. Biol. Chem. 50:957-964 and U.S. Pat. No.4,863,864. A Humicola grisea GSHE is described by Allison et al., (1992)Curr. Genet. 21:225-229 and European Patent No., 171218. The geneencoding this enzyme is also known in the art as “gla1”. An Aspergillusawamori var. kawachi GSHE is described by Hayashida et al., (1989)Agric. Biol. Chem. 53:923-929. An Aspergillus shirousami GSHE isdescribed by Shibuya et al., (1990) Agric. Biol. Chem. 54:1905-1914.

In one embodiment, a GSHE may be derived from a strain of Humicolagrisea, particularly a strain of H. grisea var. thermoidea (See, U.S.Pat. No. 4,618,579).

In some preferred embodiments, the Humicola grisea GSHE is recoveredfrom fungi including ATCC 16453, NRRL (USDA Northern Regional ResearchLaboratory, Peoria, ILL) 15219, NRRL 15220, NRRL 15221, NRRL 15222, NRRL15223, NRRL 15224 and NRRL 15225, as well as genetically altered strainsthereof. These species produce enzymatic glucoamylase preparations thatare immunologically the same (See, EP 0 171 218).

In one embodiment, a GSHE may be derived from a strain of Aspergillusawamori particularly a strain of A. awamori var. kawachi. (For examplesee, Hayashida, et al. (1989) Agric. Biol. Chem. 53:923-929).

In another embodiment, GSHEs exhibit a maximum pH activity within a pHrange of 4 to 7.5 and also within the pH range of 5 to 7.5 and maximumactivity in the temperature range of 50° C. to 60° C.

In another particularly preferred embodiment, the GSHE is a GSHEcomprising an amino acid sequence having at least 50%, 55%, 60%, 65%,70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 98% and 99% sequence identitywith the amino acid sequence set forth in SEQ ID NO:3. In anotherembodiment, the GSHE comprises an amino acid sequence having at least80% sequence identity with SEQ ID NO:3. In a further embodiment, theGSHE comprises an amino acid sequence having at least 90% sequenceidentity to SEQ ID NO:3. The GSHE may also comprises an amino acidsequence having at least 95% sequence identity with SEQ ID NO:3. In afurther embodiment, the GSHE comprises the amino acid sequence of SEQ IDNO:3.

In other embodiments, the GSHE comprising the amino acid sequence of SEQID NO:3 or an amino acid sequence having at least 80% sequence identitywith SEQ ID NO:3 is encoded by a polynucleotide having at least 70%,80%, 85%, 90%, 93%, 95%, 97%, 98% and 99% sequence identity to thesequence of SEQ ID NO:1. In a preferred embodiment, the GSHE having anamino acid sequence of SEQ ID NO:3 is encoded by a polynucleotide havingat least 70%, 80%, 85%, 90%, 93%, 95%, 97%, 98% and 99% sequenceidentity with SEQ ID NO:1. In a particularly preferred embodiment, thenucleic acid sequence encoding the GSHE of SEQ ID NO:3 is the nucleicacid sequence of SEQ ID NO:1.

In another particularly preferred embodiment, the GSHE is a GSHEcomprising an amino acid sequence having at least 50%, 55%, 60%, 65%,70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 98% and 99% sequence identitywith the amino acid sequence set forth in SEQ ID NO:6. In anotherembodiment, the GSHE comprises an amino acid sequence having at least80% sequence identity with SEQ ID NO:6. In a further embodiment, theGSHE comprises an amino acid sequence having at least 90% sequenceidentity with SEQ ID NO:6. The GSHE may also comprises an amino acidsequence having at least 95% sequence identity with SEQ ID NO:6. In afurther embodiment, the GSHE comprises the sequence of SEQ ID NO:6.

In other embodiments, the GSHE enzyme comprising the amino acid sequenceof SEQ ID NO:6 or an amino acid sequence having at least 80% sequenceidentity with SEQ ID NO:6 is encoded by a polynucleotide having at least70%, 80%, 85%, 90%, 93%, 95%, 97%, 98% and 99% sequence identity withthe sequence of SEQ ID NO:4. In a preferred embodiment, the GSHE havingan amino acid sequence of SEQ ID NO:6 is encoded by a polynucleotidehaving at least 70%, 80%, 85%, 90%, 93%, 95%, 97%, 98% and 99% sequenceidentity to SEQ ID NO:3. In a particularly preferred embodiment, thenucleic acid sequence encoding the GSHE of SEQ ID NO:6 is the nucleicacid sequence of SEQ ID NO:4.

A polynucleotide or a polypeptide having a certain percent (e.g. 80%,85%, 90%, 95%, or 99%) of sequence identity with another sequence meansthat, when aligned, that percentage of bases or amino acid residues arethe same in comparing the two sequences. This alignment and the percenthomology or identity can be determined using any suitable softwareprogram known in the art, for example those described in CURRENTPROTOCOLS IN MOLECULAR BIOLOGY (F. M. Ausubel et al. (eds) 1987,Supplement 30, section 7.7.18). Preferred programs include the GCGPileup program, FASTA (Pearson et al. (1988) Proc. Natl, Acad. Sci. USA85:2444-2448), and BLAST (BLAST Manual, Altschul et al., Natl. Cent.Biotechnol. Inf., Natl Lib. Med. (NCIB NLM NIH), Bethesda, Md., andAltschul et al., (1997) NAR 25:3389-3402). Another preferred alignmentprogram is ALIGN Plus (Scientific and Educational Software, PA),preferably using default parameters. Another sequence software programthat finds use is the TFASTA Data Searching Program available in theSequence Software Package Version 6.0 (Genetics Computer Group,University of Wisconsin, Madison, Wis.).

One skilled in the art will recognize that sequences encompassed by theinvention are also defined by the ability to hybridize under stringenthybridization conditions with the exemplified GSHE sequences (e.g., SEQID NO:1 or SEQ ID NO:4). A nucleic acid is hybridizable to anothernucleic acid sequence when a single stranded form of the nucleic acidcan anneal to the other nucleic acid under appropriate conditions oftemperature and solution ionic strength. Hybridization and washingconditions are well known in the art (See, e.g., Sambrook (1989) supra,particularly chapters 9 and 11). In some embodiments, stringentconditions correspond to a Tm of 65° C. and 0.1×SSC, 0.1% SDS.

In some embodiments of the present invention, a GSHE is produced as anextracellular enzyme by a filamentous fungal cell and particularly by aTrichoderma host that has been genetically engineered to comprise aheterologous polynucleotide encoding a GSHE derived from a Humicola sp.In preferred embodiments, the GSHE is derived from a strain of Humicolagrisea, and in some particularly preferred embodiments, the GSHE isderived from a strain of Humicola grisea var. thermoidea.

In one embodiment encompassed by the invention, the GSHE produced by theTrichoderma host (rGSHE) has at least 50%, 55%, 60%, 65%, 70%, 75%, 80%,85%, 90%, 93%, 95%, 97%, 98% or 99% sequence identity with the aminoacid sequence set forth in SEQ ID NO:3. In another embodiment, aTrichoderma host, is transformed with a heterologous polynucleotideencoding a GSHE having at least 80% sequence identity with SEQ ID NO:3.In a further embodiment, a Trichoderma host, is transformed with aheterologous polynucleotide encoding a GSHE having at least 90% sequenceidentity with SEQ ID NO:3. In another embodiment, a Trichoderma host, istransformed with a heterologous polynucleotide encoding a GSHE having atleast 95% sequence identity to SEQ ID NO:3. In other embodiments, thepolynucleotide encoding the GSHE has at least 80% sequence identity withSEQ ID NO:1 and preferably at least 95% sequence identity with SEQ IDNO:1. In a particularly preferred embodiment, the rGSHE is expressed ina Trichoderma reesei strain and has at least 80% sequence identity withthe amino acid sequence of SEQ ID NO:3.

In another preferred embodiment of the invention, the GSHE is producedas an extracellular enzyme by a filamentous fungal cell and particularlyby a Trichoderma host that has been genetically engineered to comprise apolynucleotide encoding a GSHE derived from Aspergillus sp. In someembodiments, the GSHE derived from a strain of Aspergillus awamori, andin some particularly preferred embodiments, the GSHE is derived from astrain of Aspergillus awamori var. kawachi.

In one embodiment, the GSHE produced by the Trichoderma host (rGSHE) hasat least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 98%or 99% sequence identity with the amino acid sequence set forth in SEQID NO:6. In another embodiment, a Trichoderma host is transformed with aheterologous polynucleotide encoding a GSHE having at least 80% sequenceidentity with SEQ ID NO:6. In a further embodiment, a Trichoderma hostis transformed with a heterologous polynucleotide encoding a GSHE havingat least 90% sequence identity to SEQ ID NO:6. In another embodiment, aTrichoderma host is be transformed with a heterologous polynucleotideencoding a GSHE having at least 95% sequence identity with SEQ ID NO:6.In other embodiments, the polynucleotide encoding the GSHE will have atleast 90% sequence identity with SEQ ID NO:4 and preferably at least 95%sequence identity with SEQ ID NO:4. In a particularly preferredembodiment, the GSHE is expressed in a Trichoderma reesei strain and hasat least 80% sequence identity with the sequence of SEQ ID NO:6.

In some embodiments, the level of glycosylation of a recombinantlyexpressed GSHE is different than the level of glycosylation of thecorresponding native GSHE (e.g., GSHE which was originally derived fromHumicola grisea or Aspergillus awamori has a different level ofglycosylation than the level of glycosylation of the producedrecombinant GSHE). In one embodiment, the level of glycosylation isdifferent even if the rGSHE has at least 80% amino acid sequenceidentity to the native GSHE derived from Humicola grisea or Aspergillusawamori. More specifically, in some embodiments, a rGSHE expressed inTrichoderma and particularly a strain of T. reesei has a different levelof glycosylation than the level of glycosylation from the correspondingnGSHE. In other embodiments, the level of glycosylation is higher, whilein other embodiments the level of glycosylation is lower.

In one embodiment, the level of glycosylation of the recombinantlyexpressed GSHE is lower than the level of a corresponding native GSHE.For example, the level of glycosylation for rGSHE may be at least 1%,5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% 50%, 55%, 60%, or 65% lessthan the level of glycosylation of the corresponding nGSHE. In someembodiments, the level of glycosylation in a rGSHE according to theinvention is at least 25% less than the level of glycosylation of acorresponding nGSHE. In other embodiments, the level of glycosylation ofrGSHE expressed by a host may be at least 1%, 5%, 10%, 15%, 20%, 25%,30%, 35%, 40% 50%, 60% 70%, 80%, 100%, 125%, 150%, 175%, 200%, 225% or250% greater than the level of a corresponding native form of GSHE. Insome embodiments, the level of glycosylation of rGSHE expressed by ahost is at least 100% greater that the level of nGSHE.

In another embodiment, the recombinantly produced GSHE encompassed bythe invention has greater stability at lower pH levels than acorresponding native GSHE at optimum temperature levels. Morespecifically, in some embodiments, a rGSHE expressed in Trichoderma,which was originally derived from Humicola grisea var. thermoidea, hasgreater stability at pH levels of 3.5 to 4.0 compared to a correspondingnative GSHE at temperatures of 45-55° C. For example, in one embodiment,at a pH level about 3.5 the stability of rGSHE, and particularlyHumicola grisea var. thermoidea GSHE expressed in Trichoderma reesei, ismore than double the level of stability of nGSHE from Humicola griseavar. thermoidea.

C. Vectors

According to the invention, a DNA construct comprising nucleic acidencoding a GSHE encompassed by the invention is constructed to transferGSHE into a host cell. Thus, GSHE which can be expressed in enzyme formmay be introduced into a host cell using a vector, particularly anexpression vector which comprises regulatory sequences operably linkedto a GSHE coding sequence.

The vector may be any vector which when introduced into a fungal hostcell is integrated into the host cell genome and is replicated.Reference is made to the Fungal Genetics Stock Center Catalogue ofStrains (FGSC, <www.fgsc.net>) for a list of vectors. Additionalexamples of suitable expression and/or integration vectors are providedin Sambrook et al., (1989) supra, and Ausubel (1987) supra, and van denHondel et al. (1991) in Bennett and Lasure (Eds.) MORE GENEMANIPULATIONS IN FUNGI, Academic Press pp. 396-428 and U.S. Pat. No.5,874,276. Particularly useful vectors include pFB6, pBR322, PUC18,pUC100 and pENTR/D.

In preferred embodiments, nucleic acid encoding a GSHE encompassed bythe invention is operably linked to a suitable promoter, which showstranscriptional activity in the fungal host cell. The promoter may bederived from genes encoding proteins either homologous or heterologousto the host cell. Preferably, the promoter is useful in a Trichodermahost. Suitable nonlimiting examples of promoters include cbh1, cbh2,eg/1, eg/2. In one embodiment, the promoter is one that is native to thehost cell. For example, when T. reesei is the host, the promoter is anative T. reesei promoter. In a preferred embodiment, the promoter is T.reesei cbh1, which is an inducible promoter and has been deposited inGenBank under Accession No. D86235. An “inducible promoter” is apromoter that is active under environmental or developmental regulation.In another embodiment, the promoter is one that is heterologous to thefungal host cell. Other examples of useful promoters include promotersfrom A. awamori and A. niger glucoamylase genes (See, Nunberg et al.,(1984) Mol. Cell. Biol. 4:2306-2315 and Boel et al., (1984) EMBO J.3:1581-1585). Also, the promoters of the T. reesei xln1 gene and thecellobiohydrolase 1 gene may be useful (EPA 137280A1).

In some preferred embodiments, the GSHE coding sequence is operablylinked to a signal sequence. The DNA encoding the signal sequence ispreferably that which is naturally associated with the GSHE gene to beexpressed. Preferably, the signal sequence is en coded by a Humicolagrisea or Aspergillus awamori gene which encodes a GSHE. More preferablythe signal sequence has at least 90%, at least 95%, at least 97%, and atleast 99% sequence identity to the signal sequence of depicted in FIGS.2A and 7A. In additional embodiments, a signal sequence and a promotersequence comprising a DNA construct or vector to be introduced into afungal host cell are derived from the same source. For example, in someembodiments, the signal sequence is the cdh1 signal sequence which isoperably linked to a cdh1 promoter.

In some embodiments, the expression vector also includes a terminationsequence. In one embodiment, the termination sequence and the promotersequence are derived from the same source. In another embodiment, thetermination sequence is homologous to the host cell. A particularlysuitable terminator sequence is cbh1 derived from a Trichoderma strainand particularly T. reesei. Other useful fungal terminators include theterminator from A. niger or A. awamori glucoamylase gene (Nunberg et al.(1984) supra, and Boel et al., (1984) supra).

In some embodiments, an expression vector includes a selectable marker.Examples of preferred selectable markers include ones which conferantimicrobial resistance (e.g., hygromycin and phleomycin). Nutritionalselective markers also find use in the present invention including thosemarkers known in the art as amdS argB and pyr4. Markers useful in vectorsystems for transformation of Trichoderma are known in the art (See,e.g., Finkelstein, chapter 6 in BIOTECHNOLOGY OF FILAMENTOUS FUNGI,Finkelstein et al. Eds. Butterworth-Heinemann, Boston, Mass. (1992),Chap. 6.; and Kinghorn et al. (1992) APPLIED MOLECULAR GENETICS OFFILAMENTOUS FUNGI, Blackie Academic and Professional, Chapman and Hall,London). In a preferred embodiment, the selective marker is the amdSgene, which encodes the enzyme acetamidase, allowing transformed cellsto grow on acetamide as a nitrogen source. The use of A. nidulans amdSgene as a selective marker is described in Kelley et al., (1985) EMBO J.4:475-479 and Penttila et al., (1987) Gene 61:155-164.

An expression vector comprising a DNA construct with a polynucleotideencoding a GSHE may be any vector which is capable of replicatingautonomously in a given fungal host organism or of integrating into theDNA of the host. In some embodiments, the expression vector is aplasmid. In preferred embodiments, two types of expression vectors forobtaining expression of genes are contemplated.

The first expression vector comprises DNA sequences in which thepromoter, GSHE-coding region, and terminator all originate from the geneto be expressed. In some embodiments, gene truncation is obtained bydeleting undesired DNA sequences (e.g., DNA encoding unwanted domains)to leave the domain to be expressed under control of its owntranscriptional and translational regulatory sequences.

The second type of expression vector is preassembled and containssequences required for high-level transcription and a selectable marker.In some embodiments, the coding region for a GSHE gene or part thereofis inserted into this general-purpose expression vector such that it isunder the transcriptional control of the expression construct promoterand terminator sequences. In some embodiments, genes or part thereof areinserted downstream of a strong promoter, such as the strong cbh1promoter.

Methods used to ligate the DNA construct comprising a polynucleotideencoding a GSHE, a promoter, a terminator and other sequences and toinsert them into a suitable vector are well known in the art. Linking isgenerally accomplished by ligation at convenient restriction sites. Ifsuch sites do not exist, the synthetic oligonucleotide linkers are usedin accordance with conventional practice. (See, Sambrook (1989) supra,and Bennett and Lasure, MORE GENE MANIPULATIONS IN FUNGI, AcademicPress, San Diego (1991) pp 70-76.). Additionally, vectors can beconstructed using known recombination techniques (e.g., Invitrogen LifeTechnologies, Gateway Technology).

Where it is desired to obtain a fungal host cell having one or moreinactivated genes known methods may be used (e.g. methods disclosed inU.S. Pat. No. 5,246,853, U.S. Pat. No. 5,475,101 and WO92/06209). Geneinactivation may be accomplished by complete or partial deletion, byinsertional inactivation or by any other means which renders a genenonfunctional for its intended purpose (such that the gene is preventedfrom expression of a functional protein). Any gene from a Trichoderma spor other filamentous fungal host, which has been cloned can be deleted,for example cbh1, cbh2, eg/1 and eg/2 genes. In some embodiments, genedeletion may be accomplished by inserting a form of the desired gene tobe inactivated into a plasmid by methods known in the art. The deletionplasmid is then cut at an appropriate restriction enzyme site(s),internal to the desired gene coding region, and the gene coding sequenceor part thereof is replaced with a selectable marker. Flanking DNAsequences from the locus of the gene to be deleted (preferably betweenabout 0.5 to 2.0 kb) remain on either side of the marker gene. Anappropriate deletion plasmid will generally have unique restrictionenzyme sites present therein to enable the fragment containing thedeleted gene, including the flanking DNA sequences and the selectablemarkers gene to be removed as a single linear piece.

D. Transformation of Host Cells

Introduction of a DNA construct or vector into a host cell includestechniques such as transformation; electroporation; nuclearmicroinjection; transduction; transfection, (e.g., lipofection mediatedand DEAE-Dextrin mediated transfection); incubation with calciumphosphate DNA precipitate; high velocity bombardment with DNA-coatedmicroprojectiles; and protoplast fusion. General transformationtechniques are known in the art (See, e.g., Ausubel et al., (1987),supra, chapter 9; and Sambrook (1989) supra, and Campbell et al., (1989)Curr. Genet. 16:53-56). The expression of heterologous protein inTrichoderma is described in U.S. Pat. No. 6,022,725; U.S. Pat. No.6,268,328; Harkki et al. (1991); Enzyme Microb. Technol. 13:227-233;Harkki et al., (1989) Bio Technol. 7:596-603; EP 244,234; EP 215,594;and Nevalainen et al., “The Molecular Biology of Trichoderma and itsApplication to the Expression of Both Homologous and HeterologousGenes”, in MOLECULAR I NDUSTRIAL MYCOLOGY, Eds. Leong and Berka, MarcelDekker Inc., NY (1992) pp. 129-148). Reference is also made to Cao etal., (2000) Sci. 9:991-1001 for transformation of Aspergillus strains.

Preferably, genetically stable transformants are constructed with vectorsystems whereby the nucleic acid encoding GSHE is stably integrated intoa host strain chromosome. Transformants are then purified by knowntechniques.

In one nonlimiting example, stable transformants including an amdSmarker are distinguished from unstable transformants by their fastergrowth rate and the formation of circular colonies with a smooth, ratherthan ragged outline on solid culture medium containing acetamide.Additionally, in some cases a further test of stability is conducted bygrowing the transformants on solid non-selective medium (i.e., mediumthat lacks acetamide), harvesting spores from this culture medium anddetermining the percentage of these spores which subsequently germinateand grow on selective medium containing acetamide. Alternatively, othermethods known in the art may be used to select transformants.

In one specific embodiment, the preparation of Trichoderma sp. fortransformation involves the preparation of protoplasts from fungalmycelia. (See, Campbell et al., (1989) Curr. Genet. 16:53-56). In someembodiments, the mycelia are obtained from germinated vegetative spores.The mycelia are treated with an enzyme that digests the cell wallresulting in protoplasts. The protoplasts are then protected by thepresence of an osmotic stabilizer in the suspending medium. Thesestabilizers include sorbitol, mannitol, potassium chloride, magnesiumsulfate and the like. Usually the concentration of these stabilizersvaries between 0.8 M and 1.2 M. It is preferable to use about a 1.2 Msolution of sorbitol in the suspension medium.

Uptake of DNA into the host Trichoderma sp. strain is dependent upon thecalcium ion concentration. Generally, between about 10 mM CaCl₂ and 50mM CaCl₂ is used in an uptake solution. Besides the need for the calciumion in the uptake solution, other compounds generally included are abuffering system such as TE buffer (10 Mm Tris, pH 7.4; 1 mM EDTA) or 10mM MOPS, pH 6.0 buffer (morpholinepropanesulfonic acid) and polyethyleneglycol (PEG). It is believed that the polyethylene glycol acts to fusethe cell membranes, thus permitting the contents of the medium to bedelivered into the cytoplasm of the Trichoderma sp. strain and theplasmid DNA is transferred to the nucleus. This fusion frequently leavesmultiple copies of the plasmid DNA integrated into the host chromosome.

Usually a suspension containing the Trichoderma sp. protoplasts or cellsthat have been subjected to a permeability treatment at a density of 10⁵to 10⁷/mL, preferably 2×10⁶/mL are used in transformation. A volume of100 μL of these protoplasts or cells in an appropriate solution (e.g.,1.2 M sorbitol; 50 mM CaCl₂) are mixed with the desired DNA. Generally ahigh concentration of PEG is added to the uptake solution. From 0.1 to 1volume of 25% PEG 4000 can be added to the protoplast suspension.However, it is preferable to add about 0.25 volumes to the protoplastsuspension. Additives such as dimethyl sulfoxide, heparin, spermidine,potassium chloride and the like may also be added to the uptake solutionand aid in transformation. Similar procedures are available for otherfungal host cells. (See, e.g., U.S. Pat. Nos. 6,022,725 and 6,268,328,both of which are incorporated by reference).

Generally, the mixture is then incubated at approximately 0° C. for aperiod of between 10 to 30 minutes. Additional PEG is then added to themixture to further enhance the uptake of the desired gene or DNAsequence. The 25% PEG 4000 is generally added in volumes of 5 to 15times the volume of the transformation mixture; however, greater andlesser volumes may be suitable. The 25% PEG 4000 is preferably about 10times the volume of the transformation mixture. After the PEG is added,the transformation mixture is then incubated either at room temperatureor on ice before the addition of a sorbitol and CaCl₂ solution. Theprotoplast suspension is then further added to molten aliquots of agrowth medium. This growth medium permits the growth of transformantsonly.

E. Cell Culture

Generally, cells are cultured in a standard medium containingphysiological salts and nutrients (See, e.g., Pourquie, J. et al.,BIOCHEMISTRY AND GENETICS OF CELLULOSE DEGRADATION, eds. Aubert, J. P.et al., Academic Press, pp. 71-86, 1988 and Ilmen, M. et al., (1997)Appl. Environ. Microbiol. 63:1298-1306). Common commercially preparedmedia (e.g., Yeast Malt Extract (YM) broth, Luria Bertani (LB) broth andSabouraud Dextrose (SD) broth also find use in the present invention.

Culture conditions are also standard, (e.g., cultures are incubated atapproximately 28° C. in appropriate medium in shake cultures orfermenters until desired levels of GSHE expression are achieved).Preferred culture conditions for a given filamentous fungus are known inthe art and may be found in the scientific literature and/or from thesource of the fungi such as the American Type Culture Collection andFungal Genetics Stock Center.

After fungal growth has been established, the cells are exposed toconditions effective to cause or permit the expression of a GSHE andparticularly a GSHE as defined herein. In cases where a GSHE codingsequence is under the control of an inducible promoter, the inducingagent (e.g., a sugar, metal salt or antimicrobial), is added to themedium at a concentration effective to induce GSHE expression.

F. Identification of GSHE Activity

In some embodiments, in order to evaluate the expression of a GSHE by acell line that has been transformed with a heterologous polynucleotideencoding a GSHE encompassed by the invention, assays are carried out atthe protein level, the RNA level and/or by use of functional bioassaysparticular to glucoamylase activity and/or production.

In general, assays employed to analyze the expression of a GSHE includeNorthern blotting, dot blotting (DNA or RNA analysis), RT-PCR (reversetranscriptase polymerase chain reaction), or in situ hybridization,using an appropriately labeled probe (based on the nucleic acid codingsequence) and conventional Southern blotting and autoradiography.

In addition, the production and/or expression of a GSHE may be measuredin a sample directly, for example, by assays directly measuring reducingsugars such as glucose in the culture medium and by assays for measuringglucoamylase activity, expression and/or production. Substrates usefulfor assaying GSHE activity include granular starch substrates, includingbut not limited to corn, wheat, rice, barley, tapioca, potato, andcassava. For example, in some embodiments, glucose concentration isdetermined by any convenient method such as by using glucose reagent kitNo 15-UV (Sigma Chemical Co.) or an instrument such as TechniconAutoanalyzer. In addition glucose oxidase kits and glucose hexose kitsare commercially available from Instrumentation Lab. (Lexington, Mass.).Glucoamylase activity may be assayed by the 3,5-dinitrosalicylic acid(DNS) method (See, Goto et al., (1994) Biosci. Biotechnol. Biochem.58:49-54). In one nonlimiting example, a rGSHE has the ability tohydrolyze granular starch in a 15% starch solids suspension in water toa solution of saccharides of at least 90%, 95% and/or 97% wt glucose ona dry substance basis.

In some embodiments of the invention, the GSHE expressed by arecombinant Trichoderma host is greater than 0.5 gram protein per liter(g/L) of culture medium. In some embodiments, the amount of GSHEexpressed by a recombinant Trichoderma host is greater than 1 g/L ofculture media. In some embodiments, the amount of GSHE expressed by arecombinant Trichoderma host is greater than 2 g/L of culture media. Inother embodiments, the amount of GSHE expressed by a recombinantTrichoderma host is greater than 5 g/L of culture media. Yet in otherembodiments, the amount of GSHE expressed by a recombinant Trichodermahost is greater than 10 g/L of culture medium. The amount of expressedGSHE in some instances is greater than 20 g/L, greater than 25 g/L,greater than 30 g/L and greater than 50 g/L of culture media.

In additional embodiments, protein expression, is evaluated byimmunological methods, such as immunohistochemical staining of cells,tissue sections or immunoassay of tissue culture medium, (e.g., byWestern blot or ELISA). Such immunoassays can be used to qualitativelyand quantitatively evaluate expression of a GSHE. The details of suchmethods are known to those of skill in the art and many reagents forpracticing such methods are commercially available. Exemplary assaysinclude ELISA, competitive immunoassays, radioimmunoassays, Westernblot, immunofluorescent assays and the like. In general, commerciallyavailable antibodies and/or kits may be used for the quantitativeimmunoassay of the expression level of a GSHE.

G. Methods for Purifying GSHE

In general, a GSHE produced in cell culture is secreted into the mediumand may be purified or isolated, (e.g., by removing unwanted componentsfrom the cell culture medium). In some cases, a GSHE is produced in acellular form, necessitating recovery from a cell lysate. In such cases,the enzyme is purified from the cells in which it was produced usingtechniques routinely employed by those of skill in the art. Examples ofthese techniques include, but are not limited to, affinitychromatography (Tilbeurgh et al., (1984) FEBS Lett. 16:215),ion-exchange chromatographic methods (Goyal et al., (1991) Biores.Technol. 36:37; Fliess et al., (1983) Eur. J. Appl. Microbiol.Biotechnol. 17:314; Bhikhabhai et al., (1984) J. Appl. Biochem. 6:336;and Ellouz et al., (1987) Chromatography 396:307), includingion-exchange using materials with high resolution power (Medve et al.,(1998) J. Chromatography A 808:153), hydrophobic interactionchromatography (See, Tomaz and Queiroz, (1999) J. Chromatography A865:123; two-phase partitioning (See, Brumbauer, et al., (1999)Bioseparation 7:287); ethanol precipitation; reverse phase HPLC,chromatography on silica or on a cation-exchange resin such as DEAE,chromatofocusing, SDS-PAGE, ammonium sulfate precipitation, and gelfiltration (e.g., Sephadex G-75). The degree of purification desiredwill vary depending on the use of the GSHE. In some embodiments of thepresent invention, purification will not be necessary.

H. Industrial Uses of the rGSHE—Fermentations

In some embodiments of the present invention, fungal cells expressing aheterologous GSHE are grown under batch or continuous fermentationconditions. A classical batch fermentation is a closed system, whereinthe composition of the medium is set at the beginning of thefermentation and is not subject to artificial alterations during thefermentation. Thus, at the beginning of the fermentation the medium isinoculated with the desired organism(s). In this method, fermentation ispermitted to occur without the addition of any components to the system.Typically, a batch fermentation qualifies as a “batch” with respect tothe addition of the carbon source and attempts are often made atcontrolling factors such as pH and oxygen concentration. The metaboliteand biomass compositions of the batch system change constantly up to thetime the fermentation is stopped. Within batch cultures, cells progressthrough a static lag phase to a high growth log phase and finally to astationary phase where growth rate is diminished or halted. Ifuntreated, cells in the stationary phase eventually die. In general,cells in log phase are responsible for the bulk of production of endproduct.

A variation on the standard batch system is the “fed-batch fermentation”system, which also finds use with the present invention. In thisvariation of a typical batch system, the substrate is added inincrements as the fermentation progresses. Fed-batch systems are usefulwhen catabolite repression is apt to inhibit the metabolism of the cellsand where it is desirable to have limited amounts of substrate in themedium. Measurement of the actual substrate concentration in fed-batchsystems is difficult and is therefore estimated on the basis of thechanges of measurable factors such as pH, dissolved oxygen and thepartial pressure of waste gases such as CO₂. Batch and fed-batchfermentations are common and well known in the art.

Continuous fermentation is an open system where a defined fermentationmedium is added continuously to a bioreactor and an equal amount ofconditioned medium is removed simultaneously for processing. Continuousfermentation generally maintains the cultures at a constant high densitywhere cells are primarily in log phase growth.

Continuous fermentation allows for the modulation of one factor or anynumber of factors that affect cell growth and/or end productconcentration. For example, in one embodiment, a limiting nutrient suchas the carbon source or nitrogen source is maintained at a fixed rate anall other parameters are allowed to moderate. In other systems, a numberof factors affecting growth can be altered continuously while the cellconcentration, measured by media turbidity, is kept constant. Continuoussystems strive to maintain steady state growth conditions. Thus, cellloss due to medium being drawn off must be balanced against the cellgrowth rate in the fermentation. Methods of modulating nutrients andgrowth factors for continuous fermentation processes as well astechniques for maximizing the rate of product formation are well knownin the art of industrial microbiology.

There are a wide variety of industrial uses for the recombinant GSHEproduced according to the invention. The GSHE is most useful inapplications requiring granular starch hydrolysis to sugars, for examplein the manufacture of glucose syrups and for grain processing in ethanolproduction.

EXPERIMENTAL

The following examples are provided in order to demonstrate and furtherillustrate certain preferred embodiments and aspects of the presentinvention and are not to be construed as limiting the scope thereof.Indeed, it is contemplated that these teachings will find use in furtheroptimizing the process systems described herein.

In the disclosure and experimental section which follows, the followingabbreviations apply: wt % (weight percent); ° C. (degrees Centigrade);rpm (revolutions per minute); H₂O (water); dH₂O (deionized water); aa(amino acid); bp (base pair); kb (kilobase pair); kD (kilodaltons); g(grams); μg (micrograms); mg (milligrams); μL (microliters); ml and mL(milliliters); mm (millimeters); μm (micrometer); M (molar); mM(millimolar); μM (micromolar); U (units); V (volts); MW (molecularweight); sec (seconds); min(s) (minute/minutes); hr(s) (hour/hours);PAGE (polyacrylamide gel electrophoresis); DO (dissolved oxygen);phthalate buffer (sodium phthalate in water, 20 mM, pH 5.0); PBS(phosphate buffered saline [150 mM NaCl, 10 mM sodium phosphate buffer,pH 7.2]); SDS (sodium dodecyl sulfate); Tris(tris(hydroxymethyl)aminomethane); w/v (weight to volume); w/w (weightto weight); v/v (volume to volume); Genencor (Genencor International,Inc., Palo Alto, Calif.); and Shin Nihon (Shin Nihon, Japan).

EXAMPLE 1 Cloning the H. grisea var. thermoidea GSHE Gene

Genomic DNA (SEQ ID NO:1) was extracted from frozen Scytalidiumthermophilum (ATCC 16453, anamorph, H. grisea var. thermoidea) mycelia.The frozen mycelia were ground with dry ice in a coffee grinder and theDNA was extracted by the EasyDNA protocol (Invitrogen). An extrachloroform/phenol/isoamyl alcohol extraction was added to the standardprotocol. PCR primers were designed, based on the NCBI databaseaccession #M89475 sequence. The forward primer contained a motif fordirectional cloning into the pENTR/D vector (Invitrogen).

The sequence of the RSH003f primer was CAACATGCATACCTTCTCCAAGCTCCTC (SEQID NO. 7) and the sequence of the RSH004r primer wasTTAACGCCACGAATCATTCA CCGTC (SEQ ID NO. 8).

The PCR product was cloned into pENTR/D, according to the InvitrogenGateway system protocol. The vector was then transformed into chemicallycompetent Top10 E. coli (Invitrogen) with kanamycin selection. PlasmidDNA from several clones was restriction digested to confirm the correctsize insert. The gla1 insert was sequenced (Sequetech, Mountain View,Calif.) from several clones. Plasmid DNA from one clone, pENTR/D_N13,was added to the LR clonase reaction (Invitrogen Gateway system) withpTrex3g/amdS destination vector DNA. Recombination, in the LR clonasereaction, replaced the CmR and ccdB genes of the destination vector withthe H. grisea gla1 from the pENTR/D vector. This recombinationdirectionally inserted gla1 between the cbh1 promoter and terminator ofthe destination vector. Recombination site sequences of 48 and 50 bpremained upstream and downstream, respectively, of gla1. An aliquot ofthe LR clonase reaction was transformed into chemically competent Top10E. coli and grown overnight with carbenicillin selection. Plasmid DNA,from several clones, was digested with appropriate restriction enzymesto confirm the correct insert size. Plasmid DNA from clone, pTrex3g_N13(see FIGS. 3 and 4) was digested with Xba1 to release the expressioncassette including the cbh1 promoter:gla1:cbhl terminator:amdS. This 6.6kb cassette was purified by agarose gel extraction using standardtechniques and transformed into a strain of T. reesei derived from thepublicly available strain QM6a, as further described below.

The cassette was sequenced by Sequetech, Mountain View, Calif. and theDNA for GSHE is illustrated in FIG. 1 (SEQ ID NO:1) and the amino acidsequence illustrated in FIG. 2 (SEQ ID NOs:2 and 3).

EXAMPLE 2 Transformation of T. reesei

Approximately 2 cm² of a plate of sporulated mycelia (grown on a PDAplate for 5 days at 30° C.) was inoculated into 50 ml of YEG (5 g/Lyeast extract plus 20 g/L glucose) broth in a 250 ml, 4-baffle shakeflask and incubated at 37° C. for 16-20 hours at 200 rpm. The myceliawere recovered by transferring the liquid volume into 50 ml conicaltubes and spinning at 2500 rpm for 10 minutes. The supernatant wasdecanted. The mycelial pellet was transferred into a 250 ml, 0.22 micronCA Corning filter bottle containing 40 ml of filtered β-D-glucanasesolution and incubated at 30° C., 200 rpm for 2 hrs to generateprotoplasts for transformation.

Protoplasts were harvested by filtration through sterile miracloth intoa 50 ml conical tube. They were pelleted by spinning at 2000 rpm for 5minutes and aspirated. The protoplast pellet was washed once with 50 mlof 1.2 M sorbitol, spun down, aspirated, and washed with 25 ml ofsorbitol/CaCl₂. Protoplasts were counted and then pelleted at 2000 rpmfor 5 min, the supernate was decanted, and the protoplast pellet wasresuspended in an amount of sorbitol/CaCl₂ sufficient to generate aprotoplast concentration of 1.25×10⁸ protoplasts per ml, generating aprotoplast solution.

Aliquots of up to 20 μg of expression vector DNA (in a volume no greaterthan 20 μl) were placed into 15 ml conical tubes and the tubes were puton ice. Then 200 μl of the protoplast suspension was added along with 50μl PEG solution to each transformation aliquot. The tubes were mixedgently and incubated on ice for 20 min. PEG solution (2 ml) was added tothe transformation aliquot tubes, and these were incubated at roomtemperature for 5 minutes. Sorbitol/CaCl₂ (4 ml) solution was added tothe tubes (generating a total volume of 6.2 ml). The transformationmixture was divided into 3 aliquots each containing about 2 ml. Anoverlay mixture was created by adding each of these three aliquots tothree tubes of melted top agar (kept molten by holding at 50° C.) andthis overlay mixture was poured onto a transformation plate. Thetransformation plates were then incubated at 30° C. for four to sevendays.

The transformation was performed with amdS selection. Acetamide/sorbitolplates and top agar were used for the transformation. Top agar wasprepared by the same Sorbitol/acetamide agar recipe as the plates,except that low melting agarose was used in place of Noble agar.Transformants were purified by transfer of isolated colonies to freshselective media containing acetamide (i.e., Sorbitol/acetamide agar,without sorbitol).

With reference to the examples the solutions were prepared as follows.

-   -   1) 40 ml β-D-glucanase solution was made up in 1.2M sorbitol and        included 600 mg β-D-glucanase (InterSpex Products Inc., San        Mateo, Calif.) and 400 mg MgSO₄.7H₂O.    -   2) 200 ml PEG mix contained 50 g PEG 4000 (BDH Laboratory        Supplies Poole, England) and 1.47 g CaCl₂.2H₂O made up in dH₂O.    -   3) Sorbitol/CaCl₂ contained 1.2M sorbitol and 50 mM CaCl₂.    -   4) Acetamide/sorbitol agar:        -   Part 1-0.6 g acetamide (Aldrich, 99% sublime.), 1.68 g CsCl,            20 g glucose, 20 g KH₂PO₄, 0.6 g MgSO₄.7H₂O, 0.6 g            CaCl₂.2H₂O, 1 ml 1000× salts (see below), adjusted to pH            5.5, brought to volume (300 mls) with dH₂O, filter            sterilized.        -   Part II—20 g Noble agar and 218 g sorbitol brought to volume            (700 mls) with dH₂O and autoclaved.        -   Part II was added to part I for a final volume of 1 L.    -   5) 1000× Salts−5 g FeSO₄.7H₂O, 1.6 g MnSO₄.H₂O, 1.4 g        ZnSO₄.7H₂O, 1 g CoCl₂.6H₂O were combined and the volume was        brought to 1 L with dH₂O. The solution was filter sterilized.

EXAMPLE 3 Fermentation of T. reesei Transformed with the H. grisea var.thermoidea GSHE Gene

In general, the fermentation protocol as described in Foreman et al.(Foreman et al. (2003) J. Biol. Chem. 278:31988-31997) was followed.More specifically, duplicate fermentations were run for each of thestrains displayed in FIG. 5. 0.8 L of Vogels minimal medium (Davis etal., (1970) Methods in Enzymology 17A, pg 79-143 and Davis, Rowland,NEUROSPORA, CONTRIBUTIONS OF A MODEL ORGANISM, Oxford University Press,(2000)) containing 5% glucose was inoculated with 1.5 ml frozen sporesuspension. After 48 hours, each culture was transferred to 6.2 L of thesame medium in a 14 L Biolafitte fermenter. The fermenter was run at 25°C., 750 RPM and 8 standard liters per minute airflow. One hour after theinitial glucose was exhausted, a 25% (w/w) lactose feed was started andfed in a carbon limiting fashion to prevent lactose accumulation. Theconcentrations of glucose and lactose were monitored using a glucoseoxidase assay kit or a glucose hexokinase assay kit withbeta-galactosidase added to cleave lactose, respectively(Instrumentation Laboratory Co., Lexington, Mass.). Samples wereobtained at regular intervals to monitor the progress of thefermentation. Collected samples were spun in a 50 ml centrifuge tube at¾ speed in an International Equipment Company (Needham Heights, Mass.)clinical centrifuge.

Sample supernatants were run of 4-12% BIS-TRIS SDS-PAGE gels, underreducing conditions with MOPS (morpholinepropanesulfonic acid) SDSrunning buffer and LDS sample buffer. The results are provided in FIG.5. Lanes 3, 4 and 5 illustrate a 68 kD rGSHE band at different timeperiods.

EXAMPLE 4 Assay of GSHE Activity from Transformed Trichoderma reeseiClones

Enzyme activity—GSHE activity was determined as milligrams (mg) ofreducing sugars released (measured as glucose equivalent) per minute(min) during an incubation of 5 ml of 10% granular cornstarch in a 0.1 Macetate buffer, pH 4.5, 50° C. with an aliquot of the enzymepreparation. One unit of GSHE is defined as 1.0 mg of reducing sugarreleased per min under the assay conditions.

Native GSHE (nGSHE) from Humicola grisea var. thermoidea and recombinantGSHE produced from T. reesei were purified by standard techniques usinghydrophobic interaction chromatography using phenyl-sepharose (AmershamBiosciences, Piscataway, N.J.) followed by ion exchange chromatographyusing SP-sepharose (Amersham Biosciences, Piscataway, N.J.). Therecombinant GSHE initially expressed by T. reesei clones included twoprotein peak fractions in about equal concentrations. These peaks werelabeled rGSHE1 and rGSHE2. The two peaks differed in mass by 1500D andby 0.3 pH units as measured by matrix assisted laser desorption andionization (MALDI-TOF) on a voyageur mass spectrometer (AppliedBiosystems, Foster City, Calif.) and an isoelectric focusing gel (SERVAElectrophoresis, GmbH, Heidelberg, Germany) according to manufacturerdirections. Both rGSHE1 and rGSHE2 have the same specific activity asmeasured by the raw starch hydrolyzing assay and protein measurementsusing a MicroBCA protein assay kit (Pierce, Rockford, Ill.) and thepercent solution extinction coefficient (A280 0.1%=1.963). After aperiod of time, measured at approximately 72 hours after initial rGSHEexpression, only one form of rGSHE is represented (rGSHE3). (See Table1).

TABLE 1 Specific Activity Source of GSHE GSHE Units/mg % totalcarbohydrate Native GSHE 9.0 1.12 rGSHE1/rGSHE2 8.0/8.0 2.70 rGSHE3 8.00.57

The % carbohydrate (CHO) of the GSHEs was determined by acid hydrolysisusing 4N trifluoroacetic acid at 100° C. for 5 hrs and measurements weremade of the released reducing sugars using parahydroxybenzoic acidhydrazide.

When initially expressed, the glycosylation of rGSHE1 and rGSHE2 was2.70% of the total carbohydrate. However, after 72 hours, the level ofglycosylation of rGSHE3 found in the medium was 0.57% total CHO. Thelevel of glycosylation of native GSHE was 1.12%.

EXAMPLE 5

Comparison of native GSHE from H. grisea var. thermoidea andrecombinantly expressed H. grisea var. thermoidea GSHE in Trichodermareesei.

A. pH Stability was Determined from pH 3 to 7.

The collected samples of recombinantly produced GSHE as described abovein example 3 and samples of native GSHE were diluted to equal proteinconcentrations with 20 mM acetate buffer at pH 4.5. Reactions were thenrun in 100 mM citrate/NaOH buffers at 50° C. for 30 minutes at pH levels3 to 7.

1.0 ml of the reaction was then added to 5 ml of 10% corn starch(Cargill Foods, Minneapolis, Minn.) in 100 mM acetate, pH 4.5 in sampletubes. The tubes were shaken at 50° C. for 20 minutes. Then 0.5 ml 2.0%NaOH was added. Tubes were spun and 0.5 ml of the supernatant wasassayed for reducing sugars using the Dinitro Salicylic acid (DNS) assay(Goto et al., (1994) supra,).

The results of the assay are depicted in FIG. 8A. The recombinantlyproduced GSHE exhibited about 80% residual activity at pH 3.5. Incomparison, the corresponding native GSHE exhibited only about 20%residual activity. At pH 4.0 both the recombinantly produced GSHE andthe native GSHE exhibited about 82% residual activity and at pH 5.5 bothenzymes exhibited between about 90 to 100% residual activity.

Stability was also measured at pH 7.5 to 10.5 using the methods asdescribed above. However, the buffer was 100 mM boric acid/NaOH buffer.As exhibited in FIG. 8B, at pH 7.5 both enzymes exhibited about 100%residual activity. At pH 8.5 recombinantly produced GSHE exhibited about82% residual activity and the native GSHE exhibited about 90% residualactivity. At pH 9.5 the % residual activity of recombinantly producedGSHE was substantially less than the native GSHE. (10% compared to 72%,respectively).

B. Profile of Activity as a Function of Temperature.

Temperature stability was determined at pH 5.75. Using essentially thesame procedures as described above for the pH stability studies, enzymesamples were diluted to equal protein concentrations in a 100 mM acetatebuffer and then 1.0 ml of the diluted enzymes was exposed to a waterbath temperature of 40° C., 50° C., 60° C. and 70° C. for 10 minutes andassayed as described above in the pH stability studies. The results arepresented in Table 2.

TABLE 2 Temp % GSHE Source ° C. Residual Activity Native GSHE 40 100 5095 60 90 70 0 Recombinant GSHE 40 100 50 93 60 92 70 0 % residualactivity means the % difference referenced to 100% at pH 4.0

The profile of activity as a function of temperature of therecombinantly produced GSHE is similar to that of the correspondingnative GSHE.

c. Hydrolysis of Granular Corn Starch by nGSHE and rGSHE.

Both native GSHE from H. grisea var. thermoidea (nGSHE) andrecombinantly expressed H. grisea var. thermoidea (rGSHE) in Trichodermareesei were diluted to equal protein concentrations in pH 4.5 acetatebuffer. One ml of the dilution was added to a 10% corn starch (CargillFoods, Minneapolis, Minn.) slurry in 20 mM pH 4.5 acetate buffer andshaken at 350 rpm at 50° C. At designated time intervals 100 μL ofslurry was removed and added to 10 μL of 2% NaOH. The sample was spunand the supernatant was assayed for glucose (mg glucose/mg protein)using the glucose oxidase reagent in a Monarch clinical analyzer(Instrumentation Laboratory, Lexington, Mass.). As shown in FIG. 9 thehydrolysis of corn starch was slightly lower for the rGSHE compared tothe nGSHE.

EXAMPLE 6 Cloning the Aspergillus awamori var. kawachi GSHE Gene

Genomic DNA was extracted from frozen mycelia of a strain of A. awamorivar. kawachi according to the methods described in Example 1. The PCRprimer sequences were designed based on the published sequence of the A.awamori var. kawachi glucoamylase GAI (Hayashida, et al. (1989) Agric.Biol. Chem. 53:923-929). This GAI is a GSHE. The following primers wereused: the RSH10f primer having the sequence, CAC CAT GTC GTT CCG ATC TCTTCT C (SEQ ID NO:9), which includes the Gateway (Invitrogen) directionalcloning motif CACC and the RSH11r primer having the sequence, CTA CCGCCA GGT GTC GGT CAC (SEQ ID NO:10).

The DNA sequence is provided in FIG. 6 (SEQ ID NO:4). The encoded GSHEpolypeptide sequence, including the signal peptide, is provided in FIG.7A (SEQ ID NO:5) and the mature protein sequence is provided in FIG. 7B(SEQ ID NO:6).

The 2.16 kb PCR product was gel-purified (Gel Purification kit, Qiagen)and cloned into pENTR/D (Invitrogen), according to the Gateway systemprotocol. The vector was then transformed into chemically competentTop10 E. coli (Invitrogen) with kanamycin selection. Plasmid DNA fromseveral clones was restriction digested to confirm the correct sizeinsert. The GAI gene insert was sequenced (Sequetech, Mountain View,Calif.) from several clones (SEQ ID NO:4). Plasmid DNA from one clone,pENTR/D-Ak33xx#1, was added to the LR clonase reaction (InvitrogenGateway system) with the pTrex3g/amdS destination vector DNA.Recombination, in the LR clonase reaction, replaced the CmR and ccdBgenes of the destination vector with the A. kawachi GAI from the pENTR/Dvector. This recombination directionally inserted GAI between the cbh1promoter and terminator of the destination vector. AttB recombinationsite sequences of 48 and 50 bp remained upstream and downstream,respectively, of the glucoamylase. Reference is made to FIG. 3, whereinthe H. grisea gla1 has been replaced by the A. kawachi GAI in thisexample. Two microliters of the LR clonase reaction were transformedinto chemically competent Top10 E. coli and grown overnight withcarbenicillin selection. Plasmid DNA from several clones was digestedwith Xbal to confirm the insert size. Plasmid DNA from clone,pTrex3g_Akxx #3 was digested with Xbal to release the expressioncassette including the cbhl promoter:GAI:cbhl terminator:amdS. This 6.7kb cassette was purified by agarose extraction using standard techniquesand transformed into a strain of T. reesei derived from the publiclyavailable strain QM6a.

EXAMPLE 7 Transformation of T. reesei with the A. awamori var. kawachiGSHE Gene

A Trichoderma reesei spore suspension was spread onto the center ˜6 cmdiameter of an MABA transformation plate (150 μl of a 5×10⁷−5×10⁸spore/ml suspension). The plate was then air dried in a biological hood.Stopping screens (BioRad 165-2336) and macrocarrier holders (BioRad1652322) were soaked in 70% ethanol and air dried. DriRite desiccant wasplaced in small Petri dishes (6 cm Pyrex) and overlaid with Whatmanfilter paper. The macrocarrier holder containing the macrocarrier(BioRad 165-2335) was placed flatly on top of filter paper and the Petridish lid replaced.

A tungsten particle suspension was prepared by adding 60 mg tungstenM-10 particles (microcarrier, 0.7 micron, Biorad #1652266) to anEppendorf tube. One ml ethanol (100%) was added. The tungsten wasvortexed in the ethanol solution and allowed to soak for 15 minutes. TheEppendorf tube was microfuged briefly at maximum speed to pellet thetungsten. The ethanol was decanted and washed three times with steriledistilled water. After the water wash was decanted the third time, thetungsten was resuspended in 1 ml of sterile 50% glycerol. The tungstenwas prepared fresh every two weeks.

The transformation reaction was prepared by adding 25 μl of suspendedtungsten to a 1.5 ml Eppendorf tube for each transformation. Subsequentadditions were made in order, 0.5-5 μl DNA (0.2-1 μg/μl), 25 μl 2.5MCaCl₂, 10 μl 0.1 M spermidine. The reaction was vortexed continuouslyfor 5-10 minutes, keeping the tungsten suspended. The Eppendorf tube wasthen microfuged briefly and decanted. The tungsten pellet was washedwith 200 μl of 70% ethanol, microfuged briefly to pellet and decanted.The pellet was washed with 200 μl of 100% ethanol, microfuged briefly topellet, and decanted. The tungsten pellet was resuspended, by pipetting,in 24 μl 100% ethanol. The Eppendorf tube was placed in an ultrasonicwater bath for 15 seconds and 8 μl aliquots were transferred onto thecenter of the desiccated macrocarriers. The macrocarriers were left todry in the desiccated Petri dishes.

A He tank was turned on to 1500 psi. 1100 psi rupture discs (BioRad165-2329) were used in the Model PDS-1000/He Biolistic Particle DeliverySystem (BioRad). When the tungsten solution was dry, a stopping screenand the macrocarrier holder were inserted into the PDS-1000. An MABAplate, containing the target T. reesei spores, was placed 6 cm below thestopping screen. A vacuum of 29 inches Hg was pulled on the chamber andheld. The He Biolistic Particle Delivery System was fired. The chamberwas vented and the MABA plate removed for incubation, 28° C. for 5-7days.

With reference to Example 7 the were prepared as follows.

Modified amdS Biolistic agar (MABA) per liter Part I, make in 500 mldH₂O 1000× salts 1 ml Noble agar 20 g pH to 6.0, autoclave Part II, makein 500 ml dH₂O Acetamide 0.6 g CsCl 1.68 g Glucose 20 g KH₂PO₄ 15 gMgSO₄•7H₂O 0.6 g CaCl₂•2H₂O 0.6 g pH to 4.5, 0.2 micron filtersterilize; leave in 50° C. oven to warm, add to Part I, mix, pourplates. 1000× Salts FeSO₄•7H₂O 5 g MnSO₄•H₂O 1.6 g ZnSO₄•7H₂O 1.4 gCoCl₂•6H₂O 1 g 0.2 micron filter sterilize

Expression of rGSHE (A. awamori var. kawachi GSHE expressed in T.reesei) was determined as described above for expression of H. griseavar. thermoidea in Examples 3 and 4. The level of expression wasdetermined to be greater than 1 g/L (data not shown). FIG. 10 providesthe results of a SDS-PAGE gel illustrating the expression of Aspergillusawamori var. kawachi GSHE in the T. reesei host.

It is claimed:
 1. A fermentation medium comprising a granular starchhydrolyzing enzyme (GSHE) having glucoamylase activity produced from aculture of Trichoderma reesei, wherein the Trichoderma reesei comprisesa heterologous polynucleotide encoding the GSHE, and wherein the GSHEcomprises SEQ ID NO:6.